1. Field of the Invention
The invention relates to synthetic dental compositions for the production of dental restorative structures containing one or more methacryl compounds, and to dental restorative structures produced therefrom.
2. Discussion of Prior Art
It is known to employ catalysts or initiators based on organic peroxides or benzopinacols in the preparation of synthetic dental compositions or dental restorative structures. Vinyl compounds and their polymers, for example, and in particular monomeric acrylates and methacrylates, alone or in admixture with polymers, may be used for this purpose. Examples of suitable catalysts are benzoyl peroxide (BPO), lauroyl peroxide (LPO), unsubstituted benzopinacol and 4,4'-dimethylbenzopinacol. Very often, however, the use of benzoyl peroxide entails the formation of countless minute bubbles which frequently permeate the polymerized structure uniformly. These bubbles result both in a reduction of the strength of the polymerized structure and in a diminution of its transparency. The transparency of the polymers is an important factor particularly in the case of artificial teeth, and more particularly of incisors, where even a small number of minute bubbles will render the product esthetically unacceptable. The presence of minute bubbles is undesirable also in dental prostheses and in all other polymerized restorative structures. Moreover, peroxides generally tend to decompose upon prolonged storage and to produce undesirable discoloration in the end product.
The term "synthetic dental composition" is generally applied to any polymerizable or polymerized product having no particular shape, while "dental restorative structures" refers to appropriately shaped products made from polymerizable or polymerized synthetic dental compositions, such as artificial teeth, crowns and bridges as well as prostheses and the like.
Now when benzopinacols are used in place of peroxides as catalysts in the production of synthetic dental compositions or of dental restorative structures, the risk that small bubbles will form is less pronounced; however, larger bubbles then frequently form in smaller number, in a manner not susceptible to control, during polymerization.